The purpose of this study will be to differentiate the effect of Desmopressin Acetate (DDAVP) versus Vasopressin Tannate (AVP) on the treatment of Diabetes Insipidus (DI). AVP has been associated with hypertension as a complication, but DDAVP has not. This is because there are two receptors postulated, a different on for each of these drugs. There are anecdotal reports of patients who are resistant to DDAVP. The investigators will differentiate the effects of these two drugs on controlling DI in five subjects.